Measuring Single-Molecule Conductance at An Ultra-Low Molecular Concentration in Vacuum

Abstract

We report on systematic investigation of single-molecule detection mechanisms in break junction experiments in vacuum. We found molecular feature in the conductance traces at an extremely low concentration of molecules of 10 nM. This was attributed to condensation of the molecular solution on the junction surface upon evaporation of the solvent during evacuation. Furthermore, statistical analyses of the temporal dependence of molecular junction formation probabilities suggested accumulation effects of the contact mechanics to concentrate molecules absorbed on a remote area to the tunneling current sensing zone, which also contributed to the capability of molecular detections at the low concentration condition. The present findings can be used as a useful guide to implement break junction measurements for studying electron and heat transport through single molecules in vacuum.

Dissecting Time-Evolved Conductance Behavior of Single Molecule Junctions by Nonparametric Machine Learning

“…The result can be explained by the effect of surface migration of C 8 DT molecules letting them accumulate near the electrode gap. 23 These findings are certainly not possible by the histogrambased conventional analyses that can only evaluate a major feature of molecular junctions.…”

“…These molecules bind to Au electrodes via their terminal thiol groups. Previous studies − have shown that transport through the above relatively short alkanedithiols at ambient temperature can be approximated by a nonresonant quantum tunneling process characterized by exponential dependence of the single-molecule conductance on the chain length with well-defined decay constant. We therefore considered only the tunneling contributions and assumed other factors such as charge hopping to be negligibly weak for the carbon chains employed .…”

“…In fact, the rates of the four events revealed a gradual increase in f ( G M ) and f ( G H ) and a decrease in f ( G L ) and f ( G Noise ) (Figure c). The result can be explained by the effect of surface migration of C 8 DT molecules letting them accumulate near the electrode gap . These findings are certainly not possible by the histogram-based conventional analyses that can only evaluate a major feature of molecular junctions.…”

“…Conductance versus time traces were measured using lithographed micro-MCBJs − consisting of a free-standing Au nanowire on a flexible substrate. Deflection of the substrate was controlled by a piezoelectric rod to break the Au wire at the notched location.…”

Computational investigation of unsaturated ketone derivatives as MAO-B inhibitors by using QSAR, ADME/Tox, molecular docking and molecular dynamics simulations

“…With the help of these methods, several approved drugs have been developed [23][24][25][26][27][28]. For example, the discovery of amprenavir as a potential inhibitor of the human immunodeficiency virus (HIV) protease using protein modeling and MD simulations [29], imatinib as an inhibitor of the tyrosine kinase using SBDD [30], amprenavir as a potential inhibitor of the human immunodeficiency virus (HIV) protease using protein modeling and MD simulations [31,32], thymidylate synthase inhibitor, raltitrexed against HIV using the SBDD approach [33], Norfloxacin as an inhibitor of topoisomerase II, IV using QSAR modeling [32], and darolutamide as an inhibitor of androgen receptor using docking and MD simulations [34].…”